Jerusalem has yielded one of its most remarkable secrets: the largest dam ever found in Israel, dating back nearly 2,800 years. Archaeologists say the colossal structure, uncovered in the City of David National Park, was built during a period of climate upheaval and engineered to secure the city's water supply against both drought and flood.
The discovery was made by the Israel Antiquities Authority in collaboration with the Weizmann Institute of Science. Their research, published in the journal PNAS, ties the dam's construction to the reigns of Judah's Kings Joash or Amaziah around 795-805 BCE. "This is the largest dam ever discovered in Israel and the earliest one ever found in Jerusalem," excavation directors Dr. Nahshon Szanton, Itamar Berko, and Dr. Filip Vukosavović said. Rising 12 meters high and 8 meters wide, with a visible length of 21 meters, the structure is thought to extend far beyond the current dig.
The dam was part of a broader water-management system that included a fortified tower at the Gihon Spring and a channel funneling water into the Pool of Siloam. Together, the installations reflect urban planning on a scale rarely seen in the ancient Near East.
"The collaboration between the Weizmann Institute researchers and the Israel Antiquities Authority offers new insight into the challenges faced by the inhabitants of ancient Jerusalem," said Szanton, noting that the system supplied key neighborhoods such as Mount Zion.
Dating was confirmed by analyzing twigs and branches trapped in the mortar, a method that pinpointed the construction to a decade during a severe dry spell. Prof. Elisabetta Boaretto and Dr. Johanna Regev of the Weizmann Institute said the project was clearly "a direct response to climate change and arid conditions that included flash floods."